AN international team of researchers has developed the first horse vaccine for the deadly Hendra virus, using the ovary cells of a Chinese hamster.

Being launched on Thursday in Brisbane, the vaccine's arrival follows years of testing and means the cycle of transmission between horses and humans will be broken.

Seven people have contracted Hendra and four have died from the virus that has killed 81 horses, including nine this year. There is no known cure for Hendra, which was first identified in the Brisbane suburb of Hendra in 1994.

While flying foxes transmit the virus through bodily fluids, humans have only ever contracted the virus from horses.

A specialist in veterinary pathology at the CSIRO's Australian Animal Health Laboratory in Geelong, Deborah Middleton, said that, by stopping the virus in horses, science had effectively stopped it making the leap to humans.

''This is significant, as to get a vaccine to market for people would have taken another 10 or 20 years because of all the guidelines and ethical approval needed,'' she said.

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Work on developing a vaccine didn't start until 2005, as scientists first had to understand the virus' structure, parts and how it generated an immune response from the animals it infected.

That research led scientists to focus on the many proteins found on the outside of the virus that act as an alert for the immune system. One protein in particular caught their attention - the G-protein.

''We realised it was protection against the G-protein that was really critical in clearing the virus from the system,'' Dr Middleton said.

This protein is the active ingredient in the vaccine. Once injected, animals generate antibodies to the G-protein and can eliminate infection much faster when it happens.

''It gives the animal a head start,'' Dr Middleton said. ''If you have an animal vaccinated with the G-protein, its immune system is tricked into thinking it has seen the virus before, so it already has antibodies and it can react quickly.''

The G-protein can be man-made in commercial quantities, intriguingly using a cell line derived from the ovary cells of a Chinese hamster.

''It's amazing, really,'' Dr Middleton said. ''This cell line has been going for about 60 years.''

The cells keep regenerating and the gene for the Hendra G-protein is put into the cell's DNA. It then produces Hendra G-protein, which is harvested.

The Australian Veterinary Association has recommended all horses be vaccinated, with a national vaccination register to be established. The vaccine, a course of two injections, does not cause any side effects.

The multi-disciplinary team of up to 60 researchers included virologists, molecular biologists, pathologists and protein chemists. Scientists came from the CSIRO, the Henry M. Jackson Foundation for the Advancement of Military Medicine and the Uniformed Services University of the Health Sciences in the US and commercial partner Pfizer.